Lost gas indicator for gas tube lightning arrestors

ABSTRACT

A gas tube lightning arrestor includes a glass or ceramic envelope upon the ends of which are disposed disk-type electrodes and upon the interior surface of which is deposited a coating of a dessicant electrolyte. During normal operation, the electrolyte remains inert, but upon the occurence of gas leakage, atmospheric moisture is able to leak into the envelope and react with the electrolyte rendering the same conductive, such phenomena causing talking noise and/or excessive loop conductance, the latter conditions being detectable by conventional means during the course of normal plant operations.

United States Patent 1 1 1111 3,875,465 Riedel 1 Apr. 1, 1975 [5 1 LOSTGAS INDICATOR FOR GAS TUBE 2,064,369 12/1936 Biggs 313/221 2,429,42010/1947 McMaster 313/221 LIGHTING ARRESTORS Inventor: Charles E. Riedel,Villa Park, 111.

Assignee: GTE Automatic Electric Laboratories Incorporated, Northlake,111.

Filed: Oct. 18, 1973 Appl. No.: 407,685

U.S. Cl. 317/61, 317/62 int. Cl. H02h 3/22 Field oi Search 317/61, 61.5,62; 313/220,

313/221, DIG. 5; 117/97, 95

References Cited UNITED STATES PATENTS Primary Examiner-J. D. MillerAssistant ExaminerPatrick R. Salce Attorney, Agent, or FirmRobert J.Black [57] ABSTRACT Agas tube lightning arrestor includes a glass orceramic envelope upon the ends of which are disposed disk-typeelectrodes and upon the interior surface of which is deposited a coatingof a dessicant electrolyte. During normal operation, the electrolyteremains inert, but upon the occurence of gas leakage, atmosphericmoisture is able to leak into the envelope and react with theelectrolyte rendering the same conductive, such phenomena causingtalking noise and/or excessive loop conductance, the latter conditionsbeing detectable by conventional means during the course of normal plantoperations.

8 Claims, 2 Drawing Figures LOST GAS INDICATOR FOR GAS TUBE LIGHTINGARRESTORS BACKGROUND OF THE INVENTION 1. Field of the Invention Thepresent invention relates generally to gas tube lightning arrestors andmore particularly to an improved gas tube lightning arrestor whichprovides an electrical indication of the leakage and loss of thepressurized, inert gaseous atmosphere within the arrestor.

2. Description of the Prior Art While several different types oflightning arrestors, such as for example, the carbon-block type andair-gap type, have been utilized in the past as means of protectingsubscriber and office equipment from electrical surges, moderntelephonic systems are employing gas tube lightning arrestors with everincreasing frequency, the primary reason being the increased servicelife, that is, the number of repeated surges of average magnitude whicha device can withstand without failure.

However, caution must be exercised when employing gas tube lightningarrestors for should the arrestor gastight integrity fail, the rare gaswould be lost and the internal pressure altered to substantially that ofthe ambient atmosphere, the breakdown voltage of the device beingincreased by several thousand volts and consequently the arrestor can nolonger function usefully in protecting the particular associativeequipment. A structural failure within such arrestors could occur forexample, within the vicinity of the glass-to-metal seal existing betweenthe glass tubing and the metallic electrodes. Whenever two suchradically different materials must be joined in a gas-tight sealingarrangement that is designed to last for years, various factors, such asfor example, improper bonding and unequal rates of expansion associatedwith the metal and insulator components, could eventually result instructural fatigue and failure.

In view of the foregoing, companies utilizing gas tube lightningarrestors must conduct periodic tests of the individual devices in orderto determine if they are still providing the requisite protection. Suchmeans of detecting gas leakage however is inconvenient and sometimesimpossible within telephone plants and telephonic systems.

SUMMARY OF THE INVENTION Accordingly, it is an object of the presentinvention to provide an improved gas tube lightning arrestor which willeliminate the aforementioned problems and disadvantages.

Another object of the present invention is to provide an improved gastube lightning arrestor which will automatically indicate the loss ofinert gas from the lightning arrestor.

Still another object of the present invention is to provide an improvedgas tube lighting arrestor which will provide an electrical indicationof when the inert gas pressure is lost from the arrestor, suchindication being detected by conventional means.

The foregoing objectives are achieved according to the present inventionthrough the provision of a gas tube lightning arrestor which includes aglass or ceramic envelope upon the ends of which are disposed disk-typeelectrodes and upon the interior surface of which is deposited a coatingof a dessicant electrolyte. During normal operation, the electrolyteremains inert,

but upon the occurence of gas leakage, such as for example, during alightning induced arc, upon cessation of the are, atmospheric moistureis able to leak into the envelope and react with the electrolyterendering the same conductive, such phenomena causing talking noiseand/or excessive loop conductance, the latter conditions beingdetectable by conventional means during the course of normal telephonicplant operations.

BRIEF DESCRIPTION OF THE DRAWINGS Various other objects, features, andattendant advantages of the present invention will be more fullyappreciated as the same becomes better understood from the followingdetailed description when considered in connection with the accompanyingdrawings, in which like reference characters designate like orcorresponding parts throughout the several views, and wherein:

FIG. 1 is a perspective view of a section of glass or ceramic tubinghaving a dessicant electrolyte coated upon the interior surface thereof;and

FIG. 2 is a perspective view of the tubing of FIG. 1 having suitableelectrodes sealed thereto so as to form a gas tube lightning arrestor inaccordance with the present invention.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring now to thedrawings, the gas tube lightning arrestor of the present invention isgenerally indicated by the reference character 10 and is seen to includean envelope 12 which may be either glass or ceramic tubing, disk-typemetallic electrodes I4 being disposed upon the end portions thereof andadapted for connection to appropriate circuitry. In the instance thatglass tubing is employed, the interior surface of the tubing isinitially etched or frosted in order to render the same sufficientlycoarse and adherent so as to be able to retain coated material thereon,such processes being unnecessary in the case of ceramic due to the factthat such material is inherently coarse to the requisite degree.

In preparing the envelope 12 for use within the assembled lightningarrestor 10, a solution, not necessarily aqueous, of a dessicantelectrolyte material is deposited within the tubing and subsequentlydried whereupon the entire interior surface of the tubing is able to becoated therewith, as noted at 16. Sections of tubing of several feet inlength may be so coated by dipping the same in a saturated solution,repetition of the dipping and drying processes resulting in an increasein the coating thickness, as a saturated solution will not dissolveprevious coating layers.

The exterior surfaces of the tubing sections are then washed and thesections severed so as to provide smaller tubing sections of such lengthas is desired in formulating lightning arrestors in accordance with thepresent invention. The electrodes 14 are then mounted upon the endportions of the envelopes l2 and the assemblies placed within a vacuumchamber whereupon the air being evacuated, the desired noble, inertgases, such as for example, argon, are introduced therewithin to apressure of approximately one-fourth atmosphere.

In order to provide rapid arrestor breakdown during the occurence offast-rising surges, the inert gas may contain minute traces of aradioactive element which serves to partially ionize the gas, the lowpressure within the arrestor, in addition to the use of the radioactivematerial, permitting the arrestor assemblies to exhibit breakdownvoltages equal to conventional carbon'block arrestors while theelectrode spacing is considerably greater than that existing within suchconventional arrestors. As a result of such electrode spacing, thelikelihood of electrode fragments being severed from the electrodes andbecoming lodged within the spacing or gap and thereby grounding thearrestor, is substantially lessened.

Subsequent to the introduction of the inert gas within the envelope l2,suitable sealing means, such as for example, boron nitride, may beutilized to seal the envelopc relative to the electrodes 14, whereuponthe assembly may be cured at temperatures approximating 300C in theinstance of boron nitride. During normal arrestor operation, thedessicant electrolyte [6 remains inert, and the coating thickness issuch that resistance between the electrodes 14 may be in excess of lmegohm, the thickness of course being adjustable so as to result in anyother desired resistance value.

If gas leakage should occur during a lightning induccd arc, the elevatedtemperature and pressure within the envelope normally attending alightning surge prevents the admission of air therewithin andconsequently moisture within the air is not able to react with theelectrolyte l6 and normal protector operation occurs. Upon the occurenceof quiescent conditions however, the temperature and pressure within theenvelope I2 is sharply decreased and atmospheric moisture is able toenter the envelope and react with electrolyte 16 rendering the sameelectrically conductive. The protector resistance is decreased to avalue well below I megohm within a time period ranging from minutes tohours, such resulting in the generation of talking noise and/orexcessive loop conductance, both phenomena being capable of detection byconventional means during normal plant operation. The defective arrestormay then of course be replaced.

It should be noted that during power line crossing conditions wherein ahigh current are is maintained within the arrestor for several secondsor minutes, the dessicant electrolyte may tend to fuse and react withthe glass or ceramic envelope l2 and under such conditions, conventionalsolder-pellet failsafe structures provided within such gas tubeprotectors are expected to operate so as to short-circuit the line,whereupon the protector must also be replaced. Since certain somewhatunknown levels of power cross current could fuse the dessicantelectrolyte but not cause gas leakage nor solder-pellet operation, it isadditionally important to select an envelope. material which softensnear and slightly below the fusing temperature of the dessicantelectrolyte. As a result of such selection, gas leakage and itselectrical indication, is insured prior to the destruction of thearrestor assembly.

Examples of dessicant electrolytes which may be employed within the gastube lightning arrestor of the present invention are as follows:

Thus, it may be seen that the gas tube lightning arrestor of the presentinvention has important advantages over the known prior art structuresin that the arrestor provides an automatic electrical indication of gasleakage therefrom and defective protection thereby, which may be readilydetected by conventional means, such improved arrestors therebyeliminating the need for conducting periodic testing of individuallightning arrestors within protector systems.

Obviously, many modifications and variations of the present inventionare possible in light of the above teachings. It is to be understoodtherefore, that within the scope of the appended claims, the presentinvention may be practiced otherwise than as specifically describedherein.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

l. A gas tube lightning arrestor comprising:

a tubular envelope;

a pair of electrodes respectively sealed upon the end portions of saidtubular envelope;

an inert, pressurized gas disposed within said envelope; and

means within said envelope for automatically indicating leakage of saidgas from said envelope comprising a dessicant electrolyte coated uponthe interior surface of said envelope and which during normal operationof said arrestor remains inert but upon the occurrence of leakage ofsaid gas from said envelope and admission of air within said envelope,atmospheric moisture is able to react with said electrolyte renderingthe same electrically conductive.

2. A gas tube lightning arrestor as set forth in claim I, wherein thethickness of said coating of said electrolyte may be adjusted so as toattain a particular resistance value between said electrodes.

3. A gas tube lightning arrestor as set forth in claim 1, wherein saidtubular envelope is ceramic.

4. A gas tube lightning arrestor as set forth in claim I, wherein saidtubular envelope is etched glass.

5. A gas tube lightning arrestor as set forth in claim 1, wherein saidtubular envelope is frosted glass.

6. A gas tube lightning arrestor as set forth in claim 1, wherein saidinert gas is argon.

7. A gas tube lightning arrestor as set forth in claim 1, wherein saiddessicant electrolyte is CaCl 8. A gas tube lightning arrestor as setforth in claim 1, wherein said dessicant electrolyte is in electricalcontact with each of said pair of electrodes.

1. A gas tube lightning arrestor comprising: a tubular envelope; a paIrof electrodes respectively sealed upon the end portions of said tubularenvelope; an inert, pressurized gas disposed within said envelope; andmeans within said envelope for automatically indicating leakage of saidgas from said envelope comprising a dessicant electrolyte coated uponthe interior surface of said envelope and which during normal operationof said arrestor remains inert but upon the occurrence of leakage ofsaid gas from said envelope and admission of air within said envelope,atmospheric moisture is able to react with said electrolyte renderingthe same electrically conductive.
 2. A gas tube lightning arrestor asset forth in claim 1, wherein the thickness of said coating of saidelectrolyte may be adjusted so as to attain a particular resistancevalue between said electrodes.
 3. A gas tube lightning arrestor as setforth in claim 1, wherein said tubular envelope is ceramic.
 4. A gastube lightning arrestor as set forth in claim 1, wherein said tubularenvelope is etched glass.
 5. A gas tube lightning arrestor as set forthin claim 1, wherein said tubular envelope is frosted glass.
 6. A gastube lightning arrestor as set forth in claim 1, wherein said inert gasis argon.
 7. A gas tube lightning arrestor as set forth in claim 1,wherein said dessicant electrolyte is CaCl2.
 8. A gas tube lightningarrestor as set forth in claim 1, wherein said dessicant electrolyte isin electrical contact with each of said pair of electrodes.